Umbilical cord compression associated with amniotomy: laboratory observations.

Impairment of umbilical cord blood flow has been associated with periodic fetal heart rate changes termed "variable decelerations." These patterns may be observed after amniotomy. A chronic fetal rhesus monkey preparation has been used to investigate this clinical observation. Loss of amniotic fluid produced variable deceleration patterns, while restoration of amniotic fluid volume eliminated such changes. These experimental data demonstrate that amniotic fluid may be critical in protection of the cord and maintenance of normal umbilical cord blood flow.